Because of the shortage of the petroleum energy resource and the promotion of the environment protection, people continuously and actively study the art related to the replaceable energy and the regenerative energy resources in order to reduce the dependence of petroleum energy resource and the influence on the environment. The solar cell is an attractive candidate among those replaceable energy and the regenerative energy resources because the solar cell can directly convert solar energy into electricity. In addition, there are no harmful substances like carbon oxide or nitride generated during the process of generating electricity so there is no pollution to the environment.
The basic structure of a solar-cell element includes an optoelectronic semiconductor stack layer, an upper electrode formed on the upper surface of the optoelectronic semiconductor stack layer, and a back electrode formed on the bottom surface of the optoelectronic semiconductor stack layer. Furthermore, for receiving most solar light, the upper surface of the optoelectronic stack may be covered by an anti-reflecting layer.
The solar-cell element can further connect to a base via a bonding layer to form a light-absorbing device. In additional, the base can further include at least a circuit to electrically connect to the electrode of the solar cell element via a conductive structure such as metal wire.